1. Field of the Invention
The present invention relates to a cassette system having a radiation detector for detecting a radiation that has passed through a subject and converting the detected radiation into radiation image information.
2. Description of the Related Art
In the medical field, there have widely been used radiation image capturing apparatus which apply a radiation to a subject and guide the radiation that has passed through the subject to a radiation detector so as to capture a radiation image from the radiation. Known forms of the radiation detector include a conventional radiation film for recording a radiation image by way of exposure, and a stimulable phosphor panel for storing a radiation energy representing a radiation image in a phosphor and reproducing the radiation image as stimulated light by applying stimulating light to the phosphor. The radiation film with the recorded radiation image is supplied to a developing device to develop the radiation image, or the stimulable phosphor panel is supplied to a reading device to read the radiation image as a visible image.
In the operating room or the like, it is necessary to read a recorded radiation image immediately from a radiation detector after the radiation image is captured for the purpose of quickly and appropriately treating the patient. As a radiation detector which meets such a requirement, there has been developed a radiation detector having a solid-state detector for converting a radiation directly into an electric signal or converting a radiation into visible light with a scintillator and then converting the visible light into an electric signal to read out a detected radiation image.
As shown in FIG. 12 of the accompanying drawings, Japanese Laid-Open Patent Publication No. 2004-173907 discloses a cassette (electronic cassette) 306 which is connected to a cable 302 having a connector 300 and has a battery 304, an image memory 305, and an electric board 303 on which a drive circuit, an amplifier, an A/D converter, and a serializing circuit are mounted. It also discloses an X-ray image capturing system in which a connector 310 on a cable 308 or a wireless module 330 is connected to the connector 310, a controller 314 with a power supply 312 is connected to the connector 300 by the cable 308 or a wireless terminal 322, and an X-ray generator 318 having an X-ray tube 317 is connected to the controller 314 by a cable 316. The controller 314 is combined with a monitor 320 for displaying captured images and a storage 338 for storing captured images.
The technology disclosed in Japanese Laid-Open Patent Publication No. 2004-173907 is undesirable because the cable 302 connected to the cassette 306 is awkward when the cassette 306 is carried around.
Japanese Patent No. 3494683 discloses a cassette which transmits captured radiation image information to a controller by way of wireless communications. According to the technology disclosed in Japanese Patent No. 3494683, no cable is connected to the cassette.
According to Japanese Patent No. 3494683, no cable is connected to the cassette since image data are transmitted from the cassette to the controller by way of wireless communications. However, when the cassette communicates with the controller after the cassette is set between a patient to be imaged and a bed on which the patient lies, if the directivity of an antenna of the cassette and the directivity of an antenna of the controller are not aligned with each other, then the transmission and reception sensitivity of the cassette and the controller is greatly reduced. One solution is to increase the intensity of a radio wave transmitted from the antenna of the cassette. The increased intensity of the radio wave transmitted from the antenna of the cassette necessarily results in an increase in the power consumption of the cassette. Particularly, after the cassette disclosed in Japanese Patent No. 3494683 is set between the patient and the bed, it is difficult to change the orientation of the cassette for increasing the transmission and reception sensitivity of the cassette and the controller. If the patient on the bed is seriously ill or an aged person, then it is all the more difficult to change the orientation of the cassette. There is no disclosure in Japanese Laid-Open Patent Publication No. 2004-173907 with respect to the above difficulties.
Japanese Laid-Open Patent Publication No. 2003-248060 discloses a cassette comprising a basic image capturing unit having an X-ray detecting panel and an extension device with a handle which is removably connected to the basic image capturing unit by a connector. The extension device has a battery circuit, a data recording means, and a wireless communication circuit.
The cassette disclosed in Japanese Laid-Open Patent Publication No. 2004-173907 includes electronic components such as the electric board, the image memory, etc., in addition to an X-ray detection array. The cassette disclosed in Japanese Patent No. 3494683 includes electronic components such as an image memory, a scanning pulse generator, and a transfer register in addition to a solid-state detector for detecting X-rays. The cassette disclosed in Japanese Laid-Open Patent Publication No. 2003-248060 includes electronic components such as a communication circuit and a power supply circuit in addition to the X-ray detection panel.
When X-ray images are recorded in the cassettes disclosed in Japanese Laid-Open Patent Publication No. 2004-173907, Japanese Patent No. 3494683, and Japanese Laid-Open Patent Publication No. 2003-248060, the electronic components thereof tend to be deteriorated or damaged by direct exposure to the X-rays.
For preventing the electronic components from being deteriorated or damaged, it is necessary to protect the electronic components against exposure to the X-rays with an X-ray shield such as a lead plate, for example. However, since the lead plate is heavy, it makes the cassette also heavy as a whole.